Electronic tube motor device



Dec. 14, 1948.

M. MORRISON ELECTRONIC TUBE MOTOR DEVICE 2 Sheets-Sheet 1 Filed Jam. 10,1948 Filed Jan. 10, 1948 302 33g 304' m2 5 Q 308 V 3 303 M. MORRISONELECTRONIC TUBE MOTOR DEVICE 2 Sheets-Sheet 2 Fig.4 5

w u my 501 H 5v4 CIRCUIT E CIRCUIT F CIRClI/T 6,501,506 CIOJ'ID 1x7rvuhfizvzwaz nuusueaunur Patented Dec. 14, 1948 UNITED STATES PATENTorncs Q amc'momo $310M navrca I I Montford Morrison, Upper Montclalr, N.I. Applicatio: No. 1,594

The present invention relates generally to electron discharge tubeoscillators, in particular to such oscillators when frequencystabilized, and to electric motor devices embodying such saidoscillators.

The present invention is in part a continuation of patent applicationSerial No. 599,891, filed June 16, 1945, which issued as Patent No.2,443,691, June 22, 1948, and which was a continuation in part ofapplication Serial No. 496,389, filed July 28, 1943, which issued asPatent No. 2,415,022, January 28, 1947. I

When the invention is employed as an oscillator, among the objectsthereof are; to provide a novel method of causing coupling feed-back tothe oscillatory circuit in oscillators; to provide frequencystabilization with variation plate circuit characteristics inoscillators; and particularly to provide frequency stabilization withvariation in oscillator loading. Further and other objects, when theinvention is employed as an oscillator, will be indicated and obvious tothose skilled in the art, upon reading the specification in connectionwith the drawings hereof.

When the invention is employed as an electric motor device, among theobjects thereof are; to provide an electric motor device having apredetermined speed which may be fixed with a very high degree ofaccuracy; to provide constancy in said speed with variation in theapplied motor voltage; and particularly to provide constancy in saidspeed with variation in mechanical loading of the motor. Further andother objects, when the invention is employed as an electric motordevice, will be indicated and obvious to those skilled in the art.

The nature of the invention resides importantly in the employment of twodifferent oscillatorysystems combined in tandem producing a singlefrequency or producing a single speed in a motor. One of saidoscillatory systems is set to oscillate, as an uncombined oscillator, ata frequency lower than the resonant frequency of its paralleloscillatory system, and the other of said oscillatory systems is set tooscillate, as an uncombined oscillator, at a frequency higher than theresonant frequency of its parallel oscillatory system, and the resultantcombined operation being obviously at a frequency at which the twooscillators operate in tandem. The resulting combined structure providesthe objects set forth above.

It is believed that in order to give a full, clear and exact descriptionof the invention, it will be .2 necessary to provide a fuller, clearerand more exact theory of oscillator operation, as applied to the presentinvention, than is known to the applicant in published texts. Theapplicant will provide herein such extra-conventional theory as isthought to be pertinent.

The invention will be more fully understood from the followingdescription and extra-conventional theory, when read in connection withthe accompanying drawings, of which:

Fig. 1 is a circuit diagram of one embodiment of the invention in asimple form for clearness in explaining the basic structural principlesof the invention.

Fig. 2 is a side view illustrating some detail of the type of motormechanism employed in the embodiment described herein, and shows an eddycurrent disk and its magnet both being added to the elements illustratedin the elevation shown in Fig. 1;

Fig. 3 shows a particular oscillator operating under condensive loadingand Fig. 4 and 5, are other oscillator circuits which are used inillustrating the extra-conventional theory given herein;

Figs. 6, '7 and 8 are graphs relating to the oscillators shown in Figs.3, 4, and 5 and;

Fig. 9 is a diagram illustrating the methods of making tests whichdefine certain terms used in the extra-conventional theory presentedherein.

Referring to Fig. 1, l is an alternating current motor which may be, inpractice, any one of the many types which can be made to operatesynchronously with an applied alternating voltage. The motor may be ofthe inductor type with salient poles, a direct current field type with awound rotor having no salient poles, it may be of the phonic wheel type,or any other suitable substitution.

In the embodiment shown in Fig. 1, there is employed an inductor typemotor with permanent magnetic fields and of a type commonly used as asynchronous motor and as an alternating current generator.

The stator member 2, Figs. 1 and 2, is of a laminated structure and hasa permanent magnet member 3, which provides a constant magnetic fieldfor the motor. T e teeth of the stator are so spaced angularly withreference to the teeth of the rotor 6, that the main magnetic circuitprovided'by the magnet 3, is first through coil I and then through coil4, as the rotor 6 revolves, and thus an alternating current is producedbetween terminals I and I.

Meat

The operation as described above is really that of a generator, but ofcourse, when alternating current is fed through windings 4 and I, underproper conditions, the device will act as a motor.

Referring to Fig. 2, 28 is an eddy current disk fixed to motor shaft 22,and 24 is a magnet for disk ll, constituting a loading device for motorI, in the form of the well known eddy current brake Fig. 2, 2B is avariable speed motor having a speed regulator 24 and being connectablethrough switch 21 to regulator 28 and therefore to line 28.

The simplified illustration shown in Fig. 2 forms a motor-generator setwith mechanical loading and will be understood by those familiar withthe art to which the present invention appertains.

In the prior art it has been common practice to supply motor I, withalternating current amplified up to motor requirements from anelectrically driven tuning fork. Under these conditions a high constancyoi speed control can be obtained but only at a very high apparatus costand with an excessive amount of weight. Further, under such conditionsof operation. the motor has, like all synchronous motors, a distincttendency to hunt, and while the-mean speed may have a high precision ofconstancy, the instantaneous speed may, and often does, vary badly, thusmaking such a device unsuitable for certain fields of precise work wherea complete absence of hunting and/or low apparatus cost is essential.

In Patent No. 2,415,022, the applicant disclosed a motor device whichhas a low apparatus cost, is entirely free from hunting and which may befirmly synchronized with minute injections of alternating current at, ornear, the operating frequency. However motor devices constructed on theteachings of the above patent, when unsynchronized with a stable sourceof alternating current, sometimes, require a constant loading to operateat the highest constancy of speed, that is, under certain conditions ofloading, the motor speed may change as much as a few tenths of onepercent.

In the present device when operating unsynchronized. the speed or themotor and hence the frequency of the oscillator is entirely independentof mechanical and electrical loading, within the limit of breakdowntorque of the motor, and the frequency of the system is the same for themotor stalled as for the motor run- Also with the motor stalled and thesystem operating purely as an oscillator, the frequency of the system isindependent of any reasonable electrical loading, resistive, inductiveor condensive.

Such a result in a direct current motor or in an electronic tubeoscillatory system, has not been discovered by the applicant in theprior art and is therefore considered by him as broadly new.

Further in the present system, the minimum requirement of synchronizingenergy for firmly locking in the motor with an outside source of energy,under the conditions of operation, are not certain. However indicationsare that in a two stage system, an injected energy of the order of onemillionth of the energy in the motor coils is sufilcient and probablymore than is necessary for good synchronization. Obviously the motorcoils become the oscillator output ctgrils when the system is employedas an oscilla- Such a ratio as one million to one has not beenapproached by any two stage amplification system found in the prior artby the applicant.

Referring back to Fig. 1, the winding of electric motor I, is connectedpush-pull to the output 0! twin triodes l. provided with a source ll, ofplate suppl voltage. The grids of twin triodes I are connected across acapacitance-inductance parallel oscillatory system II, the center I! ofwhich is connected with the cathods of twin triodes I.

The oscillatory system II is connected through feed-back variableresistors I3 and I4 and through capacitors II and I, when switches IIand II are'closed, to the plates of twin triodes I, which are connectedpush-pull to the windings 4 and I.

Coils 4 and I may be shunted by an electrical load I8, and may befurther shunted by a variable capacitor 24, by closing switch 2i.

Switches II and it are provided to connect and to disconnect the gridsof twin triodes I to and from the oscillatory system II and to and fromfeed-back through resistors I l and I4.

The entire circuit enclosed within dotted area A. is essentially thatshown in the above patent and may be referred to as a"retarded-oscillator" or simply as oscillator A.

oscillator which may be referred to as an "ad-- vanced-oscillator," orsimply as oscillator B.

Oscillator B has two variable plate resistors I04 and III! connectedpush-pull to the output of twin triodes Iiil, also provided with platepower supply from source It. The grids of twin triodes I09, may beconnected across parallel oscillatory system III, by closing switchesI29 and I30. The center II: of oscillatory system III is connected withthe cathodes of twin triodes I09.

The oscillatory system I I I is connected through feed-back variableresistors III and H4 and through capacitors I II and III, when switchesII! and II! are closed, to the plates of twin triodes I", which areconnected push-pull to the plate resistors I04 and IIII.

Plate resistors I04 and I may be fully or partially shunted by variablecapacitor I3I.

The output of oscillator 13 is resistance coupled to the oscillatorysystem II, of oscillator B, through capacitors II! and III and throughresistors I34 and I".

A center tapped external source of alternating current I" is providedwith current limiting variable resistors I31 and I38 and switches I39and I40. The center of source I" is connected by lead I 4| to bothoscillators at their ground potential" points.

Alternating current source I II may be connected to the grids of twintriodes 9 through leads I42 and I43, by means of switches I3! and I40;said source may be connected to the grids of twin triodes IIII throughleads I44 and I45, by means of switches i3! and I40: and said source maybe connected to the oscillatory system III, through leads I48 and I41,by means of switches Ill and I40.

It is believed that before the description of the operation of theinvention is entered into it will be necessary to define certain termsas used herein and present some extra-conventional oscillator theoryessential to a full understanding of the invention.

ings of certain terms as used herein.

To tune a circuit means to set the LC of a circuit such that the linevoltage and line current are in phase.

In resonance may mean in phase or 180 out of phase depending upon thecircuit referred to.

To setan oscillatory circuit means to fix the LC of the circuit to givethe desired result. The set LC may correspond to a value above, at, orbelow, the resonance frequency of the circuit.

The natural period of the circuit often referred to as the proper periodat which an oscillator should work, is the period of pure exoenerglcoperation of the circuit and has no direct bearing on the endoenergicoperation thereof, as will be shown hereinafter.

Exoenergic is the applicant's short term for the expression "Underconditions in which stored energy in the circuit is being given up. Theword obviously corresponds to exothermic as used in describing chemicalreactions.

Endoenergic is the applicant's short term for the expression, "Underconditions in which energy is being supplied to the circui The wordobviously corresponds to endothermic as used in describing chemicalreactions.

Endoenergic operation of any oscillatory system is commonly referred toas operation under forced oscillation, when the energy supplied is ofthe same periodic character as the oscillations forced.

However impulse driven oscilators are under endoenergic operation forthe duration of the impulse and under exoenergic operation during theabsence of the impulse.

Forced oscillators providing output energy are under both endoenergicand exoenergic operation.

Fig. 3 shows a push-pull oscillator having a resistance stabilizedfeed-back; the plate circuit has a center tapped resistor l, one set ofswitches 302 and 300 for introducing parallel variable capacitors 304and 00! across the ends of resistor 30!, and a second set of switches000 and 301 for introducing parallel variable capacitor 300 across thecentral position of resistor Ill. When switches 308 and 001 are open andswitches 302 and 303 are closed the diagram will be referred to ascircuit C. When switches I00 and 301 are closed and switches 30! and 003are open the diagram will be referred to as circuit D.

Fig. 4 shows a push-pull oscillator having a resistance stabilizedfeed-back and pure resistive loading in the plate circuits. The diagramof this figure will be referred to as circuit E.

Fig. 5 shows a push-pull oscillator having a resistance stabilizedfeed-back; the plate circuit has a split inductor l0l with a centertapped resistor 502 inserted between the split coils. This part of thediagram will be referred to as circuit .F. The figure also has a set ofswitches I00 and 504 for introducing parallel variable capacitor 50!across said split inductor; with switches I00 and 504 closed the figurewill be referred to as circuit G. The details of Figs. 6, '7 and 8 willbe discussed under the operation of Figs. 3, 4 and 5, but before theseoperations are taken up, it is necessary to establish and define certainfactors which enter into said operations, and which are explained inconnection with Fig. 9.

In Fig. 9, the part of the diagram which lies entirely outside of thedotted areas H, I and J,

' constitutes a circuit F, and while other circuits may be substitutedin its place, the illustrated circuit suffices for purposes ofillustration. The circuit F of the figure is provided with a set ofswitches SM and 002, which may be thrown to disconnect the grids of thetriodes from the oscil- Grid voltage measurement, which is employed I tomeasure voltage values and phase positions. under conditions in which.no line current and no appreciable line dc-setting" is permissible. Thisiii method is used also for obtaining the phase angle between thevoltage and the current in a parallel oscillatory system, under similarconditions. The device within dotted area H is a special A1 ampliilerwhich is constructed to have negligible phase difference between theinput and output voltages for the frequencies employed, but without anynecessarily high amplification. Such an amplifier may be constructedlike a resistancecoupled output design, but with the coupling capacitorhaving a relatively large capacity andthe output resistor having anohmic value relatively very high to that of the plate resistor. Phasedifference between the input and output can be tested by means of an"electronic switch" and a cathode ray oscilloscope.

Plate current measurements (the alternating current component thereof)are made by what may be called a "resistance drop" method. Re-

ferring to Fig. 9, the center tapped resistor 004 is a highly accuratenon-inductive resistor which is left permanently in the circuit and hassumcient resistance to give a usable reading on highresistancevolt-meter V. M. The voltmeter resistance should be of the order of 100times that of the resistor. Any direct current present in the resistoris prevented from entering the plate current measurement circuit bycapacitor 000. The

value of the current in the resistor is obviouslydetermined by thevoltmeter. For taking oscillograms and phase angle measurements of thecurrent in resistor 004, an extremely high-fidelity interstagetransformer 000, is employed having an input impedance of the order of100 times that of resistor 004. This arrangement should be checked forphase difference, because all transformers sold as high-fidelity typesmay not have a zero phase difference between the input and output forthe frequency used.

Tube voltage measurements (the alternating current component thereof)are made by a resistance drop" method but across a small percentage ofthe total resistance used, and if the total resistance used affects thecircuit constants, the shunt resistance is either left in the circuit oran equivalent resistance is substituted, so that the operation of thecircuit without the measuring device is the same as when it is in use.Referring to the circuit within the dotted area J, the total resistancebetween points 001 and 000 may be of the order of 1,000,000 ohms, theeffective resistance across the input of transformer 000, may be of theorder of 10,000. Transformer 000 is preferably an extremelyhigh-fidelity small type such as go by such trade names as 'ouncers,"inchers, and so forth, and should have an input impedance of the orderof 1,000,000 ohms.

These combinations should always be checked 7 for phase difference. With100 plate A. 0. volts 7 are made on an amplifier and obviously phaseangle measurements can be made on various parts of the circuit at anydesired frequency.

Certain experimental facts will be established on the operation of Figs.3, 4 and 5, based upon measurements taken by the circuits explained inFig 9 Referring to Fig. 4, if the voltage values and phase angle aretaken of the parallel oscillatory circuit alone of circuit E, as afunction of the applied frequency at a constant effective current, thereis obtained the familiar resonance-voltage curve III and its phase anglecurve 102, with reference to said current. If said oscillatory circultis tuned to resonance at say X cycles independently and then put intocircuit E, and the feed-back resistor properly adjusted, circuit E canbe made to oscillate at X cycles or the resonant frequency of saidoscillatory circuit.

However if the same oscillatory circuit with its I cycle resonant tuningand with the same adjustment of feed-back resistors, is substituted incircuit F and the proper measurements made, it will be found thatcircuit F does not oscillate at X cycles, but at some higher frequency8III, Fig. 8, and with a lower output with the same plate impedance,because it will be found that the grid voltage is lower.

Then if switches 50! and 504 are closed with low capacity adjustment ofcapacitor 505, it will be found that by increasing said capacity thefrequency and grid voltage can be brought to the values of circuit E.Further adjustments of said capacity will lower the grid voltage.

Now if the same oscillatory circuit with its X cycle resonant tuning andwith the same adjustment of feed-back resistors is substituted in eithercircuit C or D, say in circuit D, it will be found that circuit D doesnot oscillate at X cycles, but at some lower frequency BIII, Fig. 6, andwith a lower output with the same plate impedance, because it will befound that the grid voltage is lower.

It will be found'that other factors, like amount of feed-backresistance, Q of oscillatory circuit at the frequency and voltageemployed, and other factors which are beyond the scope essential to thisdisclosure, effect the oscillator frequency. A fuller, morecomprehensive mathematical discussion is reserved for a in a separateapplication.

From the above tests it is obvious that the circuits C, D, E, F and G,can be made to oscillate at the same frequency by employing different LCvalues in the parallel oscillatory circuits.

If the parallel oscillatory circuit of circuit F is set so that circuitF oscillates at say 600 cycles, it will be found that the oscillatorycircuit voltage values and their phase relation to the tube voltage(oscillatory circuit current) as a function of the circuit frequency, isrepresented by Fig. 8, in which the frequency corresponding to the line"I, represents 600 cycles. Assume the phase lead shown to be say 60,which is a common value. This means that the grid voltage lags the tubevoltage by 60 and that the oscillatory circuit is not operating at theresonant point, but in the steep region of the high-frequency side.

By increasing the inductance of coil 5M, that is by increasing the phaseangle between the A. C. tube current and the A. C. tube voltage, theline "I moves to the right and the operating frequency is increased, andby decreasing the inductance of coil I, the operating frequency isdecreased.

still broader disclosure tors. While in the motor just described thevariation can be made small-a few tenths of one percent-it is.nevertheless, present.

As it has been indicated, circuit C, D and G, can be adjusted so thatthe grid voltage leads the A. C. tube voltage at the operating frequencyand say this frequency is 600 cycles and is represented by the line "I,Fig. 8. Obviously increasing the shunt capacity of these circuits,decreases the frequency thereof and decreasing the capacity increasesthe frequency, within proper operating limits.

Directions can now be given for completing the detailed structure andoperation of Fig. 1. As an oscillator, the circuit is to operate, forexample, at a frequency of 600 cycles and as a motor device the motor isto operate at 1800 R. P. M. with the number of poles shown in thefigure.

First, the circuit in dotted area A is set up as shown in the area, withswitches II, ll, 2! and ill open, and with circuit B out of operation.Source I38 is set to a frequency of 600 cycles and to a voltage which,through resistors Ill and I", when switches I and Ill are closed uponleads I42 and III, will produce the normal oscillatoroperationgrid-voltage at the grids of tube I.

The motor I is brought up to above 1800 R. P. M. by closing switch 21and adjusting regulator 26, Fig. 2. After well known circuitadjustments, then switch 21 can be opened and motor I will continue torun and at 1800 R. P. M. The phase angle between the A. C. motor currentand the A. C. tube voltage is taken and recorded to be say 60".

Switches I39 and I" are opened and switches II, I8, 29 and 30 areclosed. oscillatory circuit I I and feed-back resistors are set tostable oscillator operation at 600 cycles with the motor operating (at1800 R. P. M.) with some loading by eddy current disk 23 under suitableadjustment of magnet 24, Fig. 2.

Now oscillatory circuit II, is set to a final position where theoscillator frequency and therefore the motor speed operate at a fewtenths of one percent slow, that is under 600 cycles and under 1800 R.P. M., the best value has to be found by trial after complete adjustmentof the entire system. The system is now operating in accordance with thedata shown in Fig. 8.

Second, the circuit in dotted area B is set up as shown in the area withswitches III, II, III and I30 open. Switches I39 and III are closed uponleads I46 and I41 and with source Ill operating at 600 cycles and at asuitable voltage, oscillatory circuit I II is set so that the voltagethereof leads the line current (which will be tube voltage in theoscillator) by something of the magnitude of 15 (in some casesconsiderably less suflices). Switches I39 and I" are then opened andswitches III, III, I29 and I30 are then closed with circuit A out ofoperation.

Capacitor Isl is then adjusted so that circuit B oscillates at afrequency a few tenths of one percent faster than 600 cycles.

can be substituted for Circuits A and B are then put into simultaneousoperation, and by final adjustment of feedback resistors H3 and Ill, thecombined frequency of the two systems can be brought to exactly thedesired frequency, which in the example is 600 cycles and hence themotor to exactly 1800 R. P. M. a

From the discussion of circuits C, D and F, it is obvious to thoseskilled in the art that these circuits and other circuits in thecategory of these. circuit B of Fig. l, and I hereby disclosed suchsubstitutions to be within the scope of the invention.

Under proper construction, setting and adjustments of the combined A andB circuits, the following are some of the operating characteristicswhich will be found present.

The motor speed is entirely independent of motor loading within thelimits of the breakdown torque of the motor shaft.

The oscillation frequency is entirely independent of the output circuitloading, resistive, inductive or, capacitive, within operating limits;and in view of which, the frequency is independent of whether the motoris running or not.

The system is extremely sensitive to voltages, at or near the operatingfrequency, when injected into oscillatory circuit Ill. With 3volt-amperes in motor coils I and 5, 3 micro-volt-amperes injected intooscillatory circuit III is more than is required for locking the systeminto synchronism with source I, by closing switches I3! and I40 uponleads I" and I". In a case in actual practice with switches III and I40closed and 3 micro-volt-amperes being injected into oscillatory circuitIII, with the result of firm synchronization, one of said switches couldbe opened without destroying good synchronization, so that the lowerlimit is indicated as being below 3 microvolt-amperes, or in other wordsthe ratio of injected energy to the operating is greater than one to onemillion.

While directions have been given herein to retard the independentfrequency of circuit B, a few tenths of one percent below the desiredfinal operating frequency of the system and to advance the independentfrequency of circuit A, a few tenths of one percent above the desiredfinal operating frequency of the system, these values are given only asa set of operating conditions for a starting point of flnal adjustment.These as well as other important adjustments should be made variable tofind the values which give the best results under the conditions ofdesired operation.

In the above discussion of the operation of the circuit of Fig. 1 andits equivalent circuits, directions have been given for the advancedoscillator" to be set at a frequency above normaloperating frequency forthe independent preliminary frequency value, by providing an arbitrarycondensive plate load and setting the oscillatory system to cause thedesired frequency. This procedure causes the oscillatory system tooperate at a frequency below the resonant frequency thereof, asillustrated in Fig. 6.

However the applicant has found that in practical oscillators, one maystart by setting the oscillatory system such that the normal operatingfrequency of the tandem system is below the resonant frequency (say afew percent) of the oscillatory system, and then it will be found thatby adustment of the feed-back resistors, the desired normal frequencycan be obtained with or without condensive plate loading "I.

A common structural characteristic of the two systems or methods isobviously that the advanced oscillator operates with the in tandemfrequency below the resonant frequency of its osclilatory system, andthe retarded oscillator operates with the in tandem frequency above theresonant frequencyof its oscillatory system.

A species of the invention embodying the last described structure,employing no condensive loading in the plate circuit, comprises circuitA with circuit E substituted for circuit B of Fig. 1, that is, tandemcoupled circuits -as shown in Fig. 1, with circuit A as an outputcircuit, but with circuit B eliminated and with circuit E. in its place.This combination will be referred to as circuit A-E.

An experimental study of circuit A-E' suggests an entirely differentexplanation of the theory of operation of the generic structure of theinvention, and it is believed that this different theory of operationcan be understood most readily by starting with circuits A and B asshown in Fig. 1, having been set to operate at say 600 cycles with themotor running at 1800 R. P. M., as directed in the first instance.

The feed-back circuit of circuit A is opened so that no feed-backcurrent is supplied to the grid-circuit thereof. The plate circuitcapacitance of circuit B is reduced to substantially zero, by whichprocedure circuit B becomes equivalent to circuit E, and will bereferred to as circuit E. With these settings circuit E is an oscillatorhaving its output "resistance-capacitance" coupled to the input ofcircuit A, which, under the conditions stated is operating as a specialsort of an amplifier.

The oscillatory system of circuit E is set such that the voltage thereofleads the feed-back current by a, few degrees, as a preliminary figuresubject to optimum setting say to and then the feed-back resistances ofoscillator circuit E are set to values which cause circuit E tooscillate at say 600 cycles and therefore amplifier and motor circuit Ato operate at 600 cycles. The motor will run at 1800 R. P. M., ifsufficient voltage is produced at its coil terminals. When the motor isrunning under these conditions it operates as a conventional synchronousmotor and therefore has a decided tendency to hunt.

The feed-back circuit of circuit E is now opened so that no feed-backcurrent is supplied to the grid-circuit thereof, by which procedurecircuit E is put out of operation, except for such coupling effect asits inactive circuits may have upon circuit A.

The feed-back circuit of oscillator circuit A is then closed and thefeed-back resistances thereof are set to values which cause circuit A tooscillate as at 600 cycles and the motor to run at 1800 R. P. M.

Circuit A now operates in accordance with the teaching of the abovecited patent. The frequency of oscillation of circuit A and the speed ofthe motor thereof can be set to be substantially independent of normalline voltage variations, but the frequency of oscillation, and thereforethe speed of the motor, are slightly subject to motor loading, bothpositive and negative.

In order to make it clear what is meant by positive loading and bynegative loading, assume that the eddy current brake of Fig. 2, iseliminated and that the motor of circuit A is operating at normal speed.If the speed of variable speed motor of Fig. 2, is regulated to a speedbelow said normal speed, the motor of circuit A is partially driving thevariable speed motor and may be said to be operating under positiveloading or under positive torque. If the speed of variable speed motorof Fig. 2, is regulated to a speed above said normal speed, the motor ofcircuit A is partially driven by variable speed motor and may be said tobe operating under negative loading or under negative torque.

Normally when circuit A is set to operate independently at normal speedunder normal loading, the addition of positive torque causes it to runslightly slower, and the addition of negative torque cause it to runslightly faster. However adiustments can be made to obtain differenteffects than those described.

Now with circuit A set to operate at normal frequency and the motorthereof operating at normal speed, in accordance with direction givenabove and with circuit E set to operate at normal frequency when itsfeed-back circuit is closed, said i'eed-backcircuit is then closed andthe tandem circuit operates at normal frequency and the motor operatesat normal speed, if the directions have been properly carried out.

However it will be found that the frequency of the tandem circuit, andthe speed of the motor, are not subject to variation with the additionof positive torque or with the addition of negative torque, within thebreak-down torque of the motor, and further, under usual preliminaryadjustments the frequency of the tandem circuit, and the speed of themotor, tend to decrease with increase of line voltage and to increasewith decrease of line voltage, rath..r than to go up and down with linevoltage as is an outstanding characteristic of prior art oscillators andsuch motor devices.

While the setting and adjustment of circuit A can be made by thoseskilled in the art of audiofrequency resistance stabilized oscillators,some extra-conventional theory will be helpful in setting and adjustingcircuit E, when it is employed to regulate circuit A.

In actual oscillators of the type represented by circuit E, thegenerated frequency depends importantly upon three factors-setting ofthe grid oscillatory circuit, the amount of feed-back current and theplate voltage. With the grid oscillatory circuit set for resonance at ornear the proper operating frequency of the oscillator, the generatedfrequency varies inversely with the amount of feed-back current andinversely with the plate voltage.

Of the various embodiments of the invention so farconstructed, bestresults have been obtained with the oscillation in the B circuitposition, having its oscillatory element set for resonance at afrequency which will cause the grid voltage to lead the tube voltage byan angle of the order of about 15". Different values may be moresatisfactory for different embodiments.

It will now be seen that the frequency of oscillator of circuit A varieswith the plate voltage, and that oscillator of circuit E (also ofcircuits and D) varies inversely with the plate voltage, so that thevariation of plate voltage (line voltage variation) in one oscillatoroffsets the variation in the other oscillator, which constitutesfrequency stabilization against line voltage variation.

Returning to Fig. 1 under the operating condi tion that the feed-backcircuit of circuit A is open and the tandem circuits are operatin ascoupled thereto and,

driving circuit A as an ampliner. If the phase positions of the tubevoltage in circuits E and A are taken, it will be found as to beexpected that they are apart. If, however, the feed-back circuit ofcircuit A is closed, it will be found that the phase position of thetube voltage of circuit A is pushed ahead by the output voltage ofcircuit E, and that proper operation of the tandem circuit is presentwhen the two tubes voltages are out of phase by an angle less than 180.

In view of the above discussion the operation the tandem circuit is alsoexplained by the vector combinations of the two circuits reacting oneupon the other. instead of from the pushpull" frequency standpoint.However, the two apparently different physical explanations can be shownto be mathematically equivalent.

It is believed that the directions given herein are in such clear andexact terms as will enable those skilled in the art to make and usedevices embodying the spirit of the invention, and that a much greateramount of detail would destroy the conciseness required by the rules oipractice, however some detail will be pointed out.

The circuits A and B are connected in tandem with circuit A being set topush ahead, if and when circuit B tends to lag behind the predeterminedfrequency and speed, and circuit A tends to withdraw its normalcontribution of energy to circuit B, if and when circuit B tends toadvance in frequency beyond the predetermined frequency and speed, whichof course is in fact an eflect of circuit A holding back circuit B fromadvancing in frequency. Other explanations of the operation can be givenbut it is believed that this one suffices for patent specificationpurposes.

The stability of the system in the presence of varying load isimportantly caused by the feedback current irom circuit A entering intothe oscillatory circuit Ill of circuit B. Feed-back current is, what itsname implies, opposite in phase to the forward current in the circuit.As shown in Figs. 6 and 8, the grid voltage of oscillatory circuit I llleads the grid voltage of oscillatory circuit II, but not enough to havea reversed phase position, that is, they are mostly positive at the sametime, but the feed-back voltage from circuit A, when it flows throughoscillatory circuit H I, is mostly negative when the feed-back voltagefrom circuit B is positive, so that the feed-back current from circuit Ais subtracted (vectorially) from the feed-back current from circuit B,when both currents flow through oscillatory circuit III. This means thatif the feed-back current, from circuit A in oscillatory circuit Illweakens, the resultant current therein is strengthened and circuit Btakes more control of the system with an increased forward coupled feedinto circuit A. If circuit B tends to run at a lower frequency the phasediiference in the feed-back current (vector difference) increases theforward coupling current from circuit B into oscillatory circuit ll,pullin it up to the set frequency.

The above constitutes specific embodiments of the invention and thebroader scope of the invention is pointed out with more particularity inthe claims hereunder.

I claim:

1. In an electric motor device, a first grid controlled electrondischarge tube oscillation system having an oscillatory element includedin the grid circuit of said system and an operating winding of anelectric motor included in the plate circuit oscillator circuit Ethereof, a second grid controlled electron discharge tube oscillationsystem having an oscillatory element included in the grid circuit ofsaid system and said element operating at a frequency lower than theresonant frequency thereof, and the plate circuit of said second systemcoupled to the grid circuit of said first system.

2. In an electric motor device, a first grid controlled electrondischarge tube oscillation system having an oscillatory element includedin the grid circuit of said system and an inductive winding of anelectric motor included in the plate circuit thereof, a second gridcontrolled electron discharge tube oscillation system having anoscillatory element included in the grid circuit of said system and aneffectively capacitive load circuit included in the plate circuitthereof, and said capacitive load circuit of said second system coupledto the grid circuit of said first system.

3. In an electric motor device, a first grid controlled electrondischarge tube oscillation system having an oscillatory element includedin the grid circuit of said system, said oscillatory element set tooscillate at one frequency, an operating winding of an electric motorincluded in the plate circuit of said system, a second grid controlledelectron discharge tube oscillation system having an oscillatory elementincluded in the grid circuit of said system, said oscillatory elementset to oscillate at a frequency different from first said frequency, aload included in the plate circuit of said system, and the plate circuitof said second system coupled to the grid circuit of said first system.

4. In an electric motor device, a first grid controlled electrondischarge tube oscillation system having an oscillatory element includedin the grid ci cuit of said system, said oscillatory element set tooscillate at one frequency, an operating winding of an electric motorincluded in the plate circuit of said system, a second grid controlledelectron discharge tube oscillation system having an oscillatory elementincluded in the grid circuit of said system, said oscillatory elementset to oscillate at a frequency different from first said frequency, aload included in the plate circuit of said system, and said loadincluding said oscillatory element of first said system.

5. In an electric motor device, a first grid controlled electrondischarge tube oscillation system having an oscillatory element includedin the grid circuit of said system, said oscillatory element set tooscillate at a frequency higher than the resonant frequency thereof, anoperating winding of an electric motor included in the plate circuit ofsaid system, a second grid controlled electron discharge tubeoscillatory system having an oscillatory element included in the gridcircuit of said system, said oscillatory element set to oscillate at afrequency lower than the resonant frequency thereof, an effectivelycapacitive load included in the plate circuit of said system, and theplate circuit of said second system coupled to the grid circuit of saidfirst system.

6. An electric motor device comprising an alternating current motordriven at a speed determined by the frequency of the output current oftwo grid controlled electron discharge tube oscillators coupled intandem, one of said oscillators having its uncoupled oscillationfrequency set to operate at a frequency above first said frequency, andthe other of said oscillators having its uncoupled frequency set tooperate at a frequency below first said frequency.

'7. An electric motor device comprising an alternating current motordriven at a speed determined by the frequency of the output current oftwo grid controlled electron discharge tube oscillators coupled intandem, each of said oscillators having an oscillatory element and eachof said elements being set to a different resonant frequency, theoscillator providing said output current having a circuit supplyingfeed-back current to the other of said oscillators, and last saidoscillator having its oscillatory element set to reflect said feed-backcurrent back to first said oscillator at a phase angle opposingfrequency shift in said oscillator.

8. An electric motor device comprising an alternating current motordriven at a speed determined by the frequency of the output current oftwo grid controlled electron discharge tube oscillators coupled intandem, each of said oscillators having an oscillatory element and eachof said elements being set to operate at difierent oscillationfrequencies, and coupling means between two said oscillators causing thegeneration of said output current at a frequency between said setoscillation frequencies of said two oscillatory elements.

MON'ITURD MORRISON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,563,084 Harris Nov. 24, 19251,580,536 Rosenbaum Apr. 13, 1926 2,248,481 Shuttig July 8, 19412,427,920 Morrison Sept. 23, 1947

